1. Field of the Invention
The present invention relates to an image forming apparatus with photosensors for detecting an original size. More specifically, the present invention relates to an image forming apparatus such as an electrophotographic copying machine, facsimile or the like which includes a platen cover mounted to be opened or closed with respect to a platen on which an original is put and a plurality of reflection type photosensors are embedded in the platen cover.
2. Description of the Prior Art
One example of such kind of image forming apparatus is disclosed in, for example, Japanese Patent Application Laid-open No. 73623/1979 laid open on Jun. 13, 1979. In addition, one example of a copying machine in which reflection type photosensors are actually embedded in a platen cover is known as "XEROX 5030" (commodity name). As similar to a copying machine disclosed in Japanese Patent Application Laid-open No. 73623/1979, in this copying machine, reflection type photosensors are embedded in the platen cover and a size of an original put on the platen is automatically detected by the photosensors. In addition, in order to detect whether or not the platen cover is closed with respect to the platen, the product is provided with a detection switch which is turned on or off in response to opening or closing of the platen cover. The detection switch is actuated in response to that an actuator thereof is pressed by the platen when the platen cover is closed, whereby it is possible to detect that the platen cover is closed by the detection switch.
However, in the product having such a detection switch, there are disadvantages as set forth in the following. More specifically, when a thick original such as a book is put on the platen, since the platen cover can not be completely closed, the detection switch is not actuated, and therefore, erroneous detection that although the platen cover is closed by an operator, a copying process can not be started. In addition, since the above described detection switch is a mechanical switch which has an actuator, configuration of the platen cover to which such a mechanical switch is to be mounted becomes complex. Furthermore, since a special switch is needed, cost of the product becomes high.